Niloak is koalin spelled backwards.  It was produced in Benton, Arkansas, USA by the Niloak Company from 1909 until 1946.  They h ad transitioned into contract work for the military during World War II.  When those contracts ended they made an effort to resume production of their pre-war pottery, without much success.  At that point they transitioned into a tile company with some success.

In their early  years they produced, and patented, a type of pottery they called Missionware.  Their process blended different color clays with shapes that went well with the Mission Style of the then popular Arts & Crafts movement.  Missionware looks really nice sitting on a fumed oak Stickley product.

Missionware is enjoying a resurgence in popularity and  prices have risen accordingly.  In fact, there is little or no interest in their other art pottery.  Below are links to some Niloak Pottery, Missionware items currently for sale on Ebay.  Follow the links to see larger pictures of what is for sale.  You might also want to follow some of the auctions to get a feel for current market prices.